Ingredients
Equipment
Method
- Preheat your oven to 375°F (190°C).
- Melt the butter in a large oven-safe skillet or Dutch oven over medium heat. Add the onions, salt, and pepper. Cook for 20 to 25 minutes, stirring often, until the onions are deeply caramelized.
- Stir in the thyme and garlic. Cook for 1 minute, then sprinkle the flour over the onions. Stir and cook for another 1 to 2 minutes.
- Pour in the wine, scraping up any browned bits from the bottom of the pan, and cook until the liquid has mostly evaporated, about 2 minutes. Stir in the beef broth and bring the mixture to a simmer.
- Meanwhile, cook the pasta in a large pot of salted boiling water until it is just shy of al dente. Drain the pasta well.
- Add the drained pasta to the onion mixture and stir to coat everything evenly. Sprinkle the Gruyère, mozzarella, and Parmesan cheese over the top.
- Transfer the skillet to the oven and bake for 15 to 20 minutes, until the cheese is melted and bubbly.
- Serve the pasta hot. Garnish with extra thyme if you wish.
Nutrition
Notes
Be patient when cooking the onions; the deep flavor develops as they cook down until they are jammy and golden. If you skip the wine, use extra beef broth instead; it works well. Make sure you salt the pasta water well, as the sauce itself is mild. Gruyère provides the classic French onion flavor, mozzarella helps with melting, and Parmesan adds sharpness.